JavaScriptCore-1218.tar.gz

[apple/javascriptcore.git] / API / JSManagedValue.h

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+/*
+ * Copyright (C) 2013 Apple Inc. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
+ * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
+ * THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef JSManagedValue_h
+#define JSManagedValue_h
+
+#import <JavaScriptCore/JSBase.h>
+
+#if JSC_OBJC_API_ENABLED
+
+@class JSValue;
+@class JSContext;
+
+// JSManagedValue represents a "conditionally retained" JSValue. 
+// "Conditionally retained" means that as long as either the JSManagedValue 
+// JavaScript value is reachable through the JavaScript object graph
+// or the JSManagedValue object is reachable through the external Objective-C 
+// object graph as reported to the JSVirtualMachine using 
+// addManagedReference:withOwner:, the corresponding JavaScript value will 
+// be retained. However, if neither of these conditions are true, the 
+// corresponding JSValue will be released and set to nil.
+//
+// The primary use case for JSManagedValue is for safely referencing JSValues 
+// from the Objective-C heap. It is incorrect to store a JSValue into an 
+// Objective-C heap object, as this can very easily create a reference cycle, 
+// keeping the entire JSContext alive. 
+NS_CLASS_AVAILABLE(10_9, 7_0)
+@interface JSManagedValue : NSObject
+
+// Convenience method for creating JSManagedValues from JSValues.
++ (JSManagedValue *)managedValueWithValue:(JSValue *)value;
+
+// Create a JSManagedValue.
+- (id)initWithValue:(JSValue *)value;
+
+// Get the JSValue to which this JSManagedValue refers. If the JavaScript value has been collected,
+// this method returns nil.
+- (JSValue *)value;
+
+@end
+
+#endif // JSC_OBJC_API_ENABLED
+
+#endif // JSManagedValue_h